//qoj8728
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

const int N = 6010;
int n, m;
const ll P = 1e9 + 7;
const ll i2 = 5e8 + 4;
ll C[N][N];
ll fac[N];
ll pw2[N], ipw2[N];
ll ans = 0;

int main(){
	scanf("%d%d", &n, &m);
	C[0][0] = fac[0] = pw2[0] = ipw2[0] = 1;
	for(int i = 1; i <= 2 * max(n, m); ++ i){
		C[i][0] = C[i][i] = 1;
		pw2[i] = pw2[i-1] * 2 % P;
		fac[i] = fac[i-1] * i % P;
		ipw2[i] = ipw2[i-1] * i2 % P;
		for(int j = 1; j < i; ++ j){
			C[i][j] = (C[i-1][j] + C[i-1][j-1]) % P;
		}
	}
	for(int b = 0; b <= n; ++ b){
		for(int d = 0; d <= m; ++ d){
			int a = n - b;
			int c = m - d;
			if(a + b + b != c + d + d){
				continue;
			}
			ll tmp = 0;
			for(int p = 0; p <= min(b, d); ++ p){
				ll tt = (p&1) ? P - 1 : 1;
				tt = tt * C[b][p] % P * C[d][p] % P * fac[p] % P * pw2[p] % P;
				tt = tt * fac[c+d*2-p*2] % P;
				tmp = (tmp + tt) % P;
			}
			tmp = tmp * C[n][b] % P * C[m][d] % P * ipw2[b] % P * ipw2[d] % P;
			// printf("%d %d %lld\n", b, d, tmp);
			ans = (ans + tmp) % P;
		}
	}
	printf("%lld\n", ans);
	return 0;
}